In recent years, a high-power, high-efficiency, and small radio-frequency device and a transceiving module including the same are used in the use of a radar, a satellite communication, or the like. Some of the devices and the transceiving modules manage hundreds of watts of power according to conditions.
In the current radar systems, it is important to construct a phased array system including hundreds to thousands of transceiving modules arranged in parallel for spatial control of radar beams.
It is therefore preferable to increase the performance of each transceiving module and reduce the size thereof. To realize such a transceiving module, there is a technique of forming components constituting the transceiving module as monolithic microwave integrated circuit (MMIC) chips and mounting the MMIC chips on a multilayer wiring board.
An example of related art is disclosed in H. Hommel et al., “Current Status of Airborne Active Phased Array (AESA) Radar Systems and Future Trends”, IEEE MTT-S International Microwave Symposium digest 2005, vol. 3, pp. 1449-1452.
A radio-frequency device for, for example, a radar frequency band around 10 GHz and power levels of several watts and a transceiving module including the device have not faced any challenges. Recent trends toward higher power, higher efficiency, and reduction in size have highlighted the following challenge.
To realize a high-power, high-efficiency, and small radio-frequency device and a transceiving module including the device, a high-power amplifier (HPA) in MMIC chip form (hereinafter, referred to as an “HPA-MMIC chip”) of a wide band gap semiconductor material, such as gallium nitride (GaN), may be used.
Such an HPA-MMIC chip considerably generates heat. To dissipate heat, therefore, an opening, indicated at 101, for a metal stage (hereinafter, “metal stage opening”) may be provided in a multilayer wiring board 100, a metal stage (heat spreader) 102 may be disposed in the metal stage opening 101, and an HPA-MMIC chip 103 may be disposed on the metal stage 102, as illustrated in FIG. 14.
Unfortunately, it is difficult to prevent an increase in temperature of the HPA-MMIC chip 103 because the thermal resistance of the metal stage 102 is high.
Particularly in a case where an HPA-MMIC chip is mounted on a high thermal conductivity substrate, such as a silicon carbide (SiC) substrate in consideration of crystal structure and heat dissipation, a heat dissipation path tends to spread in the in-plane direction (lateral direction). Accordingly, the thickness of the metal stage contributes to an increase in thermal resistance. Disadvantageously, the metal stage is inadequate to serve as a heat spreader.
Although the challenge related to the case where the HPA is used to construct the radio-frequency device and the transceiving module including the device has been described above, the challenge is not limited to this case. A case where a semiconductor device which generates heat is used to construct an electronic apparatus has to address a similar challenge.